Typical hydraulic systems have a hydraulic reservoir (i.e. a hydraulic fluid storage tank) that stores excess hydraulic fluid that is used by the system. The hydraulic fluid is a working fluid that is typically used to drive hydraulic cylinders, pumps, hydraulic motors or other devices for performing desired operations. Typically, the hydraulic systems will include a hydraulic pump to pressurize the fluid as it passes through the system to provide adequate power to drive the devices of the system. Additionally, hydraulic systems typically reuse the hydraulic fluid such that the hydraulic fluid is drawn from the storage tank passed through the system and then deposited back into the storage tank where it is held until it is reused by the system again.
To prevent debris or impurities from repeatedly passing through the system, prior art storage tanks 10, such as illustrated in FIG. 1, typically include a return flow filter 12 that may be either internal to the tank (as shown) or external to the tank (not shown) that filters the return fluid (illustrated as arrows 14) prior to the fluid being mixed with the rest of the clean fluid 16 being stored in the fluid tank 10. Unfortunately, when a device within the system fails, debris created due to the failure of the failed component enters the hydraulic system and is transferred back to the storage tank 10.
To prevent the system from running dry of fluid or from creating a back pressure on the system, many systems include a bypass valve 17 (either within the filter 12 itself or the reservoir 18 in which the filter 12 is housed, as shown in FIG. 1) that allows fluid 20 to bypass the filter 12, or at least the filter media of the filter 12, when the return flow filter 12 becomes spent. Unfortunately, when the bypass valve 17 opens, this permits the large debris 21 from any component failure to pass into the clean fluid storage area 22 of the storage tank 10. This debris 21 then has the opportunity to reenter the hydraulic system, which can result in further damage to the hydraulic system.
To prevent this debris 21 from again passing through the system, the storage tank 12 typically includes a baffle 24 that impedes the debris from reaching fluid outlet 26 (also known as a suction port). Additionally, the fluid outlet 26 or suction port is typically protected by a strainer 28, which is basically a coarse screen. Unfortunately, the baffle plate 24 and strainer 28 can be expensive and when the strainer 28 becomes clogged, pumps within the hydraulic system begin to run dry from fluid or are not otherwise sufficiently supplied with fluid such that the pumps begin to cavitate or otherwise degrade.
The present invention relates to improvements over the current state of hydraulic storage tanks that incorporate a fluid bypass that allows fluid to bypass the return flow filter.